The Montreal Protocol for the protection of the ozone layer, signed in October 1987, mandates the phase-out of the use of chlorofluorocarbons (CFCs). Materials more “friendly” to the ozone layer, such as hydrofluorocarbons (HFCs), e.g., HFC-134a, replaced chlorofluorocarbons. However, these latter compounds have proven to be greenhouse gases capable of causing global warming and are now regulated by the Kyoto Protocol on Climate Change. The emerging replacement materials, hydrofluoropropenes, were shown to be environmentally acceptable, having zero ozone depletion potential (ODP) and low (much less than 150) global warming potential (GWP).
Currently proposed replacement refrigerants for hydrofluorocarbons such as HFC-134a include HFC-152a, pure hydrocarbons such as butane or propane, as well as “natural” refrigerants such as CO2. Many of these suggested replacements are flammable and/or have low energy efficiency. Therefore, new alternative refrigerants are being sought. Fluoroolefin materials such as hydrofluoropropenes and/or hydrochlorofluoropropenes have generated interest as replacements for HFCs. The inherent chemical instability of these materials in the lower atmosphere provides the low global warming potential and zero or near zero ozone depletion properties desired. However, such inherent instability leads to degradation of such compounds during storage, handling and use in the presence of oxygen-containing substances such as air and water. Degradation generates acidic substances, which can result in the corrosion of equipment being used to store, handle or apply the fluoroolefins and which can catalyze further degradation.